1

Page #

What is Biology?

Biology is the study of living things, including microscopic life, plants, and animals

WHAT IS LIFE?

All living things share certain characteristics:

  • Organized: Atoms ---> molecules ---> cells ---> community
  • Genetic Code: DNA
  • Homeostasis: Maintain a stable internal environment (temperature)as outside environment changes (hot/ cold)
  • Metabolism: Take in energy from environment, transform it and use it
  • Movement: Respond to the environment (search for food, evade predators)
  • Growth: develop and mature
  • Reproduce: cell division or mating
  • Adapt to environment: must change to survive as environment changes.

THE CELL

Introduction

  • The 3 rules of The Cell Theory:
  1. The cell is the basics unit of life.
  2. All living things are made of one or more cells.
  3. All cells are produced from other cells by cell division.
  • The cell is the smallest unit that can carry out activities needed for life (the functional unit of life).
  • Cells have an outer surface called a cell membrane that shields the inside of the cell.
  • Cell membranes have “gates” that allow materials in and out ofcell.

Cell Types

  • Two major types of cells evolved:
  1. ProkaryoticCells
  2. Small simple cells that lack a nucleus andhave been around for billions of years.
  3. Prokaryotic cells’ DNA is in a single circular DNA molecule that is not surrounded by a membrane.
  4. Organisms that are made up of a single prokaryotic cell are called prokaryotes
  5. Prokaryotes are made up of only one cell-bacteria are the only kind of prokaryotes around today.
  1. Eukaryotic cells
  2. Large complex cells that contain internal parts called organelles that have their own membrane.
  3. Eukaryotic cells also have a nucleus which contains DNA and acts as the control center of the cell.
  4. Organisms with eukaryotic cells are called eukaryotes.
  5. Eukaryotes are usually made up of many cells, like people, dogs, fish, plants, etc.
  6. Sometimes though they are living one cell organisms like fungi or protist.
  • Similarities:Eukaryotes and prokaryotes both have a mostly fluid internal environment called the cytoplasm and both make proteins with small internal structures call ribosomes. (Also both have DNA and a cell membrane.) One major difference is size:

Eukaryotic Cells Have Compartments

  • These internal structures are called organelles that carry out necessary functions for the cell to survive.
  • This is just like your body contains different specializedorgans that perform necessary functions for you to survive.(Examples?)
  • Organelles are specialized compartments inside a cell that perform specialized functions such as supplying energy, packaging and delivery products, etc. so the cell and/ or organism can survive.
  • Organelles are contained in the cytosol which is the liquid part of the cytoplasm in the cell.

Organelles: A Cell’s Laborers

  • The nucleus directs cell activities: control “brain” center of the cell-
  • The nucleus stores the cells DNA in structures called chromosomes.
  • The nucleus is encased in a double membrane called the nuclear envelope.
  • The nucleus contains anucleolus which makes ribosomes.
  • The mitochondria is the “powerhouse” of the cell-
  • Converts food into energyin a process called cellular respiration.
  • The cell uses this energy to “power” its activities.
  • The endoplasmic reticulum(ER) looks like many folded sheets.
  • Sometimes ribosomes that make protein appear as little round specks on the ER: the ER then looks rough (R) and is called theRough Endoplasmic Reticulum RER.
  • When there are no ribosomes on the ER, the ER appears smooth(S) and is called the Smooth Endoplasmic Reticulum SERwhich provides a location for lipids (fats) to be made.
  • The Golgi apparatusis the “post office” of the cell.
  • The Golgi apparatus labels molecules such as proteins.
  • The Golgi apparatus thenpackages theses molecules for transport around or out of the cell.
  • Ribosomes are the site of protein synthesis (proteins being made).
  • Lysosomes are organelles that digest material such as nutrients, waste and disease causing bacteria.
  • Vacuoles- saclike structures that store materials such aswater, food and waste products.

Plant Cells Differ From Animal Cells in 4 major ways:

  1. Plants have bigger and strongervacuoles - so they can store more waterthatcreates pressurewhich helps plants stand upright (when there is less water, plants wilt).
  2. Plant cells contain chloroplasts - Chloroplasts convert energy from the sun into energy for the plant in a process called photosynthesis.
  3. Plants have rigid cell walls- These cell walls provide a thick outer layer made of protein and cellulose for protection and support.
  4. Animals, but not plants, have centrioles - cylinder looking structures which are help cells divide and multiply so we can grow.